Steering device for travelling web

ABSTRACT

A steering device for a travelling web is described which comprises a system of rotatable rollers having an approach roller, at least one steering roller and a departure roller; the axes of the approach and departure rollers are parallel to each other and fixed and the axis of the stearing roller is diplaceable, from a position parallel to that of the other rollers, in one place, and the ends of the rollers to the system are so arranged that the travelling wet laps each of the approach, steering and departure rollers in turn. The steering roller comprises a rotatable main portion over which the web laps when the axis of the steering roller is parallel to those of the other rollers, and at least one extension roller portion is axially connected to an end of the rotatable main portion and is separably rotatable; and a spindle is connected to each such extension roller portion present, and each spindle located in a guide member containing a parallel sided slot, the parallel sides of which are so positioned in relation to the approach and departure rollers that the spindle therein is displaceable only along the tangent of an ellipse constructed on the ends of the approach and departure rollers as foci and passing through the end of the stearing roller. Means for biassing each spindle present towards that end of the slot in which the spindle is located which is the approach end in regard to the travelling web are also provided.

United States Patent 11 1 Ridley Dec. 4, 19 73 STEERING DEVICE FOR TRAVELLING WEB [75] Inventor: Kenneth Arthur Ridley, Ilford,

England [73] Assignee: Iliord Limited, Essex, England [22] Filed: Dec. 21, 1972 21 Appl. No.: 317,363

9 Primary Examiner--Allen N. Knowles Assistant Examiner-Gene A. Church Attorney-E. F. Wenderoth et al.

[57] ABSTRACT A steering device for a travelling web is described which comprises a system of rotatable rollers having an approach roller, at least one steering roller and a departure roller; the axes of the approach and departure rollers are parallel to each other and fixed and the axis of the stearing roller is diplaceable, from a position parallel to that of the other rollers, in one place, and the ends of the rollers to the system are so arranged that the travelling wet laps each of the approach, steering and departure rollers in turn. The steering roller comprises a rotatable main portion over which the web laps when the axis of the steering roller is parallel to those of the other rollers, and at least one extension roller portion is axially connected to an end of the rotatable main portion and is separably rotatable; and a spindle is connected to each such extension roller portion present, and each spindle located in a guide member containing a parallel sided slot, the parallel sides of which are so positioned in relation to the approach and departure rollers that the spindle therein is displaceable only along the tangent of an ellipse constructed on the ends of the approach and departure rollers as foci and passing through the end of the stearing roller. Means for biassing each spindle present towards that end of the slot in which the spindle is located which is the approach end in regard to the travelling web are also provided.

9 Claims, 10 Drawing Figures PATENTEUDEE Mm 3.776.442

SHEET 3 OF 5 PATENTED 41975 SHEET 4 0F 5 FIGS.

' l STEERING DEVICE FOR TRAVELLING -WEB This invention relates to a steering device for travelling web material.

When web material follows a complicated path through, for example, a processing or coating apparatus it is usually required that the web be guided through the apparatus. The usual means for driving and supporting webs in processing or coating apparatus is by means of rollers. If the web departs from its normal path, i.e. if it tracks badly, it may partially or completely ride off a driving or supporting roller and become damaged. Further most web materials are reeled up after processing or coating and if the web is tracking badly just before it is reeled a badly formed reel will result which will be difficult to pack and liable to be damaged. If the web material is a film web it is possible to guide the path of the web using flanged rollers, however, flanged rollers cannot be used when the web is of paper material as the edges could be torn by contact with the flanges. In fact very serious tracking problems are more likely to occur with paper material than with film material because when paper material is wetted, for example in a coating process, the papers'tretches but often not equally along each edge. Further when wetted paper is dried stresses are set up in the paper again due to differential stretching of the paper.

In British patent specification No. l,l99,754 there is described a method of correcting the deviation of a moving web from a true or preselected path which comprises passing the web in turn around an approach roller, at least one steering roller or leading and trailing parallel spaced rollers which are mounted for pivotal movement together about an axis which is substantially coincident with and directionally aligned with the centreline of the web leaving the trailing roller, the rollers being so arranged that a line perpendicular to each roller axis and equidistant from the ends of each roller intersects the said axis, sensing the edge of the web, and pivoting the leading and trailing rollers about the said axis in accordance with the sensed position of the edge of the web so that the said line is the same distance from the edge of the web passing onto the leading roller as the said axis is from the same edge of the web leaving the trailing roller, whereby the guide rollers are moved to meet-the web rather than the guiding apparatus comprising a roller attemptingto move the web from its displaced position back to thescentreline. However, as a consequence, tight or loose edges of the web are unavoidably formed, depending on whether the axis of the guide roller being pivoted to meet the displaced web is turned toward or away from the corresponding portion of the last preceding or next following roller in apparatus for processing the web.

It is an objectof the present invention to provide a steering device for travelling web material which is free from the aforesaid drawbacks and which is of particular use in apparatus for' the treatment of paper in web form.

According to the present invention there is provided a'steering device for a travelling web whichcomprises three rotatable rollers, the approach roller, the steering roller and the-departure roller, the ends of which are arranged in triangular configuration so that the travelling web partially laps each roller in turn, the axes of the approach and departure rollers being parallel to each other and fixed, the axis of the steering roller being movable in one plane, the said steering roller having a rotatable portion over which the web laps, there being axially connected to at least one end of this portion a separately rotatable extension end piece and there being axially connected to the or each extension end piece a spindle which is located in a parallel sided slot in a slot-containing member which is so positioned in relation to the approach and departure rollers that the slot constrains the spindle located therein to move only along the tangent of the ellipse constructed on the ends of the approach and departure rollers as foci and passing through the end of the steering rollers, there being provided means to bias the or each spindle towards that end of the slot in which it is located which is the approach end in regard to the travelling web.

Preferably the slot-containing member or members are located at right angles to the axis of the steering roller.

Preferably the means used for biasing the or each spindle towards the approach end of the slot in which it is located is a coil spring, one end of which is connected to the spindle and the other end of which is connected to the slot-containing member or mounting thereof.

Preferably the steering roller is equidistantly spaced from the other two rollers. Most preferably in operation the angle made by the web as it partially laps the steering roller is The steering device of the present invention acts to steer a travelling web and prevent it tracking to one or other side of its path. It is an essential feature of the device that the slot is correctly positioned because it is so positioned that it constrains the spindle located therein to move only along the tangent of the ellipse constructed on the ends of the approach and departure rollers as foci and passing through the end of the steering roller so that in operation the total length of web between the upstream and downstream rollers remains unchanged whatever the position of the spindle in the slot and thus no tight or loose edge of the web is formed. Also the resultant force of the web tension acts at right angles to the direction of travel of the spindle and therefore does not directly influence the spindle to move in either direction along the slot. However this resultant force does serve'to hold the spindle firmly in contact with the side of the slot over which it rolls.

In the web steering device of the present invention there may be, as hereinbefore stated, either only one extension end piece to the rotatable portion of the steering roller over which the web partially laps or both ends of this portion may have an extension end piece. A device of the present invention which has two such extension end pieces differs slightly in some details and in operation from a device of the present invention which has only one such extension end piece, although in essence the devices operate in the same manner.

Thus, in one embodiment of the present invention there is provided a steering device for a travelling web which comprises, three rotatable rollers, the approach roller, the steering roller and the departure roller, the ends of which are arranged in triangular configuration so that the travelling web partially laps each roller in turn, the axes of the approach and departure rollers being parallel to each other and fixed, the axis of the steering roller being movable in one plane, the axis of the steering roller being in normal operation parallel to the axis of the other two rollers, the said steering roller having a rotatable central portion over which the web laps, there being axially connected to each end of this portion a separately rotatable extension end piece, each extension end piece having axially connected thereto a spindle which is located in a parallel sided slot in a slot-containing member, this member being so positioned in relation to the approach and departure rollers that the slots constrain the spindles located therein to move only along the tangent of the ellipse constructed on the ends of the approach and departure rollers as foci and passing through the end of the steering roller, there being provided means to bias each spindle towards that end of the slot in which it is located which is the approach end in regard to the travelling web.

In operation of the device of this embodiment of the invention the path of the web is such that it partially laps each of the three rollers. Initially the web laps only the central portion of the steering roller, the axis of which is parallel to the other two rollers of the device. Only this portion rotates, the end pieces remaining stationary. As the web continues to travel through the apparatus which contains the steering device it will probably track to one side or other of the middle roller and the side of the web will then contact one of the end extension pieces. This causes the end extension piece contacted to rotate; the direction of rotation of which is such to cause the spindle attached to that end piece to roll along the constraining slot at its point of contact, thus moving the steering roller as a whole, and altering the angle of the axis of this roller in one plane compared with the other two rollers. The axis of the steering roller is then no longer at right angles to the line of the approaching web and the web starts to return to the right angle position by returning to the central portion of the steering roller. The roller then returns, under action of the biassing means, to its normal position in the slot.

Often paper webs which have been wetted tend to curl at their edges. When this happens the edges of the web might fail to make contact with the extension end pieces if the end pieces were the same diameter as the central portion. Thus the diameter of the end pieces may be greater than the diameter of the central portion of the steering roller. There may be a slight step between the end pieces and the central portion of the steering roller or if the diameter of the end pieces is required to be appreciably greater than the diameter of the central portion then this step is tapered. Such end pieces are shown in FIGS. 6 and 7 of the accompanying drawings.

In this embodiment of the invention the length of the central portion of the steering roller defines the limits to which the base will track. If the device is to be used just before a reeling point, i.e. a point at which very precise tracking of the web is required in order to obtain a good reel, then the length of the central portion must be only slightly longer, e.g. one or two mm that the width of the travelling web. However when the steering device is used in a position when less precise tracking can be tolerated the central portion can be a two to five cm wider than the web being steered. Thus in this embodiment of the invention the steering device can be used only to steer webs within a narrow range of widths; this width depending on the length of the central portion of steering roller.

However in another embodiment of the invention webs of a greater range of widths may be steered.

In this embodiment of the present invention there is provided a steering device for a travelling web which comprises three rotatable rollers, the approach roller, the steering roller and the departure roller, the ends of which are arranged in triangular configuration so that the travelling web partially laps each rollers in turn, the axes of the departure and the approach roller being parallel to each other and fixed, the axis of the steering roller being movable in one plane and tilted at a small angle in relation to the axis of the other two rollers, the said steering roller having a rotatable portion over which the web laps, one end of which is supported in a fixed, self-aligning bearing and there being axially connected to the other end of this portion a separately rotatable extension end piece which has connected thereto a spindle which is located in a parallel sided slot in a slot-containing member, this member being so positioned in relation to the approach and departure rollers that the slot constrains the spindle located therein to move only along the tangent of the ellipse constructed on the ends of the approach and departure rollers as foci and passing through the end of the steering roller, there being provided means to bias the spindle towards that end of the slot in which it is located, which is the approach end in regard to the travelling web, the angle at which the axis of the steering roller is tilted in relation to the axes of the other two rollers being such as to cause the web to track at all times towards the rotatable extension end piece.

In the operation of this embodiment of the invention the path of the web is such that it partially laps each of the three rollers in turn. Initially the web laps only the central portion of the steering roller. Only this portion rotates, the end piece remaining stationary. As the web travels through the apparatus it will track towards the extension end piece, by virtue of the biassing tilt built into the steering roller, until its edge contacts the extension end piece. This causes the extension end piece to rotate in a direction of rotation such as to cause that end of the spindle to roll along the constraining slot at its point of contact, this moving the steering roller as a whole and altering the angle of the axis of this roller in one plane, compared with the other two rollers. The web will then start to return to the right-angle position by returning to the central portion of the roller. The roller then returns, under the action of the biassing means, to its normal position in the slot. The web will again track towards the extension end piece by virtue of the biassing tilt and the process is repeated. The total effect, therefore, is that the edge of the web on the side carrying the extension end piece is constrained to track close to a line of contact defined by the position of the gap between the central portion and the extension end piece. The biassing tilt is chosen to be sufficient to prevent the web from deviating away from the end piece.

In this embodiment of the invention any width of web can be accommodated which is shorter than the length of the rotatable portion of the steering roller.

Thus when there is only one extension end piece associated with the steering roller, the axis of the latter is caused to lie at an angle to the position of parallelism with the axes of the other rollers, the angle being chosen to be the minimum required for biassing the web to track towards the end piece.

The accompanying drawings will serve to illustrate the invention.

FIG. 1 is a perspective view of an embodiment of the steering device of the present invention having two extension end pieces and showing a travelling web passing over it.

FIG. 2 is a cross sectional view .of a steering roller of use in the same embodiment of the steering device of the present invention.

FIG. 3 is a top plan view of the same embodiment of the steering device of the present invention in operation.

FIG. 4 is also a top plan view of the same steering device of the present invention in operation.

FIG. 5 is an enlarged view of an extension end piece showing a spindle located in a slot.

FIG. 6 shows an enlarged extension end piece.

FIG. 7 shows an enlarged and tapered end piece.

FIG. 8 is a schematic illustration of the spatial inter relation of the three rollers.

FIG. 9 is a perspective view of an embodiment of the steering device of the present invention having only one extension end piece showing a travelling web pass ing over it and FIG. 10 is a cross sectional view of the steering roller shown in FIG. 9.

In FIG. 1 a travelling web 1 is shown in operation travelling in the direction indicated by the arrow thereon. The travelling web 1 is passing through a web steering device which comprises an upstream roller 2, a middle roller 3 and a downstream roller 4. The axes of the rollers 2, 3 and 4 are located parallel to each other and the ends of these rollers are in triangular configuration. The web 1 partially laps each of the rollers 2, 3 and 4 which are each freely rotatable, but are not driven.

The middle roller 3 comprises a central portion 7 and two extension end pieces 8 and 9. (This is more clearly shown in FIG. 2). Attached to each of the end pieces 8 and 9 is a respective spindle l1, 10. The spindles 10 and 11 are located in respective slots 12 and 13 respectively formed in slot plates 15, 14. Each spindle 10 and 11 is constrained to locate at the upstream end of its respective locating slot by coil springs 16, one end of each of which is attached to the end of each of the spindles l0 and 11 and the other is attached to the slot plate mounting (not shown).

In this Figure the web 1 is shown tracking centrally in the middle of the roller 3, Le. no portion of the web laps either of the end extension pieces 8 or 9.

In FIG. 2 there is shown an enlarged sectional view of the middle roller 3 of FIG. 1. In this figure the middle roller 3 is shown to comprise a central portion 7. Connected to the central portion 7 by means of respective pairs of ball races are the two extension pieces 8 and 9. Attached to the extension end piece Sis the spindle l1. Attached to the extension end piece 9is the spindle 10.

FIG. 3 is a top plan view of the steering device of FIG. 1.

The numbers have the same signification as in FIG. 1. The travelling web 1 is shown partially lapping the three rollers 2, 3 and 4. The web 1 is shown tracking centrally over the middle roller 3 and, as in FIG. 1, no portion of the web 1' laps over either of the extension pieces 8 or 9.

In FIG. 4 there is shown the same view of the device as shown in FIG..3 and the same numbers having the same signification as previously.

In this Figure a-web is shown tracking slightly to one side and a portion of this web is shown lapping the extension end piece 9. This causes the spindle 10 to move as shown in the Figure and thus the axis of the roller 3 is no longer parallel to the axes of the rollers 2 and 4. This causes the web to return to the central portion 7 of the roller 3. The spindle is then caused to return to its original position by the action of the coil spring 16.

In FIG. 5 there is shown a spindle 10 attached to the extension end piece 9. The web I is shown passing over the roller 3 and in contact with the extension end piece 9. The direction of rotation of the spindle 10 is indicated by the arrow thereon. The slot 12 in which the spindle 10 is located is also shown in this figure.

This Figure shows that when the web 1 partially laps the extension end piece 9 the spindle 10 is caused to rotate and advance in the direction indicated along the slot 12.

In FIG. 6 there is shown another steering roller having a central portion 25 and to one end an extension end piece 26 having a spindle 27. A small radial step is shown between the end piece 26 and the central portion 25.

In FIG. 7 there is shown another steering roller having a central portion 30 having attached thereto at one end an extension end piece 31 having a spindle 32 attached to it. In the case of the roller of this Figure the diameter of the major portion of the end piece 31 is greater than that of the central portion 30, there being a tapered transition to the edge of the extension end piece 31 which abuts the central portion 30.

The middle rollers shown in the last two Figures are for use when the edges of the web is likely to be curled. Thus when the path of the web moves over to lap the extension end pieces the edge of the web would contact the extension end piece even though it be curled.

In FIG. 8 there is shown the imaginary ellipse which is formed on the two rollers 2 and 4 as in FIG. 1 as foci of the ellipse and which passes through roller 3. The location of either one of the slots 12 or 13 is indicated by the arrow passing through the centre of the roller 3, this being a tangent to the ellipse which is indicated by the dotted line. For a given configuration of rollers 2, 3 and 4, the constructed ellipse is unique, as also is the tangent line at roller 3. The location of the slot indicated by-the arrow is therefore uniquely determined by the positions of rollers 2, 3, 4.

The embodiment shown if FIGS. 9 and 10 is essentially similar to thatshown in FIGS. 1 and 2, and like parts have been given like reference numbers.

The modifications consist in that the portion 8a of the steering roller 3 is no longer formed as an end piece relatively rotatable with respect to the centre portion 7 but is of one piece therewith; its spindle 11 is received as a good fit in a hole 13 in the plate 14. Thus the portion is, in effect, supported in a fixed, self-aligning bearing. The end piece 9 and its associated parts 10, 12, 15, 16 and 20 are identical with the correspondingly numbered parts in FIGS. 1 and 2.

A further modification is this embodiment is that the axis of the roller 3 is not parallel with the axes of rollers 2, 4 but lies at a small angle thereto. This angle is so chosen that in use a web 1 passing over the roller 3 will be biased to track towards the end piece 9. On contact between the web 1 and the end piece 9, the latter will rotate and cause its spindle 10 to roll in the slot 12, thereby displacing the roller 3 as a whole. The angular displacement of the roller 3 will cause the web 1 to return to the central portion 7 of the roller 3 and the spring 16 will then pull the spindle back to its normal position, whereby the movement of the web 1 can repeat itself, as just described, with the net effect of 5 keeping the web within desired path limits.

I claim:

1. A steering device for a travelling web which comprises a system of rotatable rollers having an approach roller, at least one steering roller and a departure roller, the axes of said approach and departure rollers being parallel to each other and fixed and the axis of the steering roller being displaceable, from a position parallel to that of said other rollers, in one place, the ends of the rollers in said system being so arranged that the travelling web laps each of said approach, steering and departure rollers in turn, said steering roller comprising a rotatable main portion over which the web laps when the axis of said steering roller is parallel to those of the other rollers, and at least one extension roller portion axially connected to an end of said rotatable main portion and being separably rotatable, a spindle connected to each such extension roller portion present, and for each spindle a guide member containing a parallel sided slot wherein said spindle is located, the parallel sides of said slot being so positioned in relation to said approach and departure rollers that the spindle therein is displaceable only along the tangent of an ellipse constructed on the ends of the approach and departure rollers as foci and passing through the end of the steering roller, and means for biassing each spindle present towards that end of the slot in which the spindle is located which is the approach and in regard to the travelling web.

2. A steering device as described in claim 1 wherein said slot-containing guide member present is located at right-angles to the axis of the steering roller.

3. A steering device as described in claim 1 wherein the means used for biassing the or each spindle towards the approach end of the slot in whice it is located is a coil spring, one end of which is connected to the spindle and the other end of which is connected to the slotcontaining member or mounting thereof.

4. A steering device as described in claim 1 wherein the steering roller is equidistantly spaced from the other two rollers.

5. A steering device as described in claim 1 wherein, in operation, the angle made by the web as it partially laps the steering roller is 6. A steering device as described in claim 1, wherein said steering roller comprises a rotatable control portion over which said web laps when the axis of said steering roller is parallel to those of the other rollers, and two extension roller portions axially connected to opposite ends of said central portion and being separable rotatable ends with regard to said central portion and to each other, one of said spindles connected to each of said extension roller portion and one of the said guide members for each of said spindles.

7. A steering device as described in claim 6 wherein the diameter of the end pieces of the steering roller is greater than the diametervof the centrol portion of the steering roller.

8. A steering device as described in claim 7 wherein the step between the end pieces of the steering roller and the centrol portion of the steering roller is tapered.

9. A steering device as described in claim 1, wherein the axis of said steering roller is tilted at a small angle in relation to the axes of the other two rollers, and wherein one end of the rotatable main portion of said steering roller is supported in a fixed, self-eligning beering and there is axially connected to the other end of the main portion said separately rotatable extension roller portion, the angle at which the axis of the steering roller is tilted in relation to the axes of the other two rollers being such as to cause the web to track at all times towards the rotatable extension roller portion. 

1. A steering device for a travelling web which comprises a system of rotatable rollers having an approach roller, at least one steering roller and a departure roller, the axes of said approach and departure rollers being parallel to each other and fixed and the axis of the steering roller being displaceable, from a position parallel to that of said other rollers, in one place, the ends of the rollers in said system being so arranged that the travelling web laps each of said approach, steering and departure rollers in turn, said steering roller comprising a rotatable main portion over which the web laps when the axis of said stEering roller is parallel to those of the other rollers, and at least one extension roller portion axially connected to an end of said rotatable main portion and being separably rotatable, a spindle connected to each such extension roller portion present, and for each spindle a guide member containing a parallel sided slot wherein said spindle is located, the parallel sides of said slot being so positioned in relation to said approach and departure rollers that the spindle therein is displaceable only along the tangent of an ellipse constructed on the ends of the approach and departure rollers as foci and passing through the end of the steering roller, and means for biassing each spindle present towards that end of the slot in which the spindle is located which is the approach and in regard to the travelling web.
 2. A steering device as described in claim 1 wherein said slot-containing guide member present is located at right-angles to the axis of the steering roller.
 3. A steering device as described in claim 1 wherein the means used for biassing the or each spindle towards the approach end of the slot in whice it is located is a coil spring, one end of which is connected to the spindle and the other end of which is connected to the slot-containing member or mounting thereof.
 4. A steering device as described in claim 1 wherein the steering roller is equidistantly spaced from the other two rollers.
 5. A steering device as described in claim 1 wherein, in operation, the angle made by the web as it partially laps the steering roller is 90*.
 6. A steering device as described in claim 1, wherein said steering roller comprises a rotatable control portion over which said web laps when the axis of said steering roller is parallel to those of the other rollers, and two extension roller portions axially connected to opposite ends of said central portion and being separable rotatable ends with regard to said central portion and to each other, one of said spindles connected to each of said extension roller portion and one of the said guide members for each of said spindles.
 7. A steering device as described in claim 6 wherein the diameter of the end pieces of the steering roller is greater than the diameter of the centrol portion of the steering roller.
 8. A steering device as described in claim 7 wherein the step between the end pieces of the steering roller and the centrol portion of the steering roller is tapered.
 9. A steering device as described in claim 1, wherein the axis of said steering roller is tilted at a small angle in relation to the axes of the other two rollers, and wherein one end of the rotatable main portion of said steering roller is supported in a fixed, self-eligning beering and there is axially connected to the other end of the main portion said separately rotatable extension roller portion, the angle at which the axis of the steering roller is tilted in relation to the axes of the other two rollers being such as to cause the web to track at all times towards the rotatable extension roller portion. 